What are base cores and what do they do?

Base cores are necessary in order to build a new base. Base Power Cores are required for the first three bases (1, 5, 15). Base Fusion Cores are required for the second three bases (5, 15, 25) and Base Plasma Core are required for the final three bases (10, 25, 45). When you make a new outpost, the base core is not consumed; they are only required to begin construction. Base Cores are randomly dropped when raiding bases, both from other players and NPCs. They can also be purchased from the in-game store under the Items tab.